Pure BS.
If that was not the case then there would have been no statisitcal difference from pre and post invasion Iraq. Whether or not we agree with it, the perception in the Arab world is that we're a foriegn invading army, and that propaganda is what's used to induce new recruits. Otherwise, we'd be seeing suicide bombers in places other than Iraq.
Before Iraq, the only experience the U.S. had with suicide bmobers was every couple of years. Now we get it daily, and only in Iraq. That's significant, and the cause is obvious. How to handle it is more complicated, of course, but before we can fix a problem we need to figure out what causes it.